Apparatus for the production of contact lenses

ABSTRACT

There is provided a mold comprising a male and a female mold member fabricated from thermoplastic polymeric materials which, in very thin sections are flexible under polymerization conditions, but, under said conditions are sufficiently inflexible in thick sections to retain their shape and surface characteristics. Said mold is provided, on either the male or the female member with a thin rim which, during the polymerization process, flexes and permits the old members to approach each other and compensate for the shrinkage that occurs during polymerization. Said thin rim further forms the edge of the finished lens.

FIELD OF THE INVENTION

Production of contact lenses by casting processes.

BACKGROUND OF THE INVENTION

The primary problem to overcome in utilizing a closed mold system forcasting of objects such as contact lenses where surface appearance, edgeregularity and surface finish are important is the compensation for theinevitable shrinkage that occurs on polymerization. With most monomericmaterials the volumetric shrinkage on polymerization is in the range of12 to 22%. This shrinkage has heretofore prevented satisfactory castingof objects such as contact lenses from vinyl monomers such as acrylateand methacrylate esters, vinyl pyrollidone, substituted or unsubstitutedacrylamides or methacrylamides and the like. For example, as taught inU.S. Pat. No. 3,660,545 (col 1 & 2) a polymerizing acrylate, ormethacrylate ester mixture held in a closed glass mold invariably wouldpull away from at least one mold surface and cause the formation ofsurface voids which rendered the cast object unsuitable as a lens.

In a further prior art method, (see U.S. Pat. No. 3,660,545) thepolymerizing mixture was held between concave and convex glass moldmembers having an annular gap interposed between them which decreased aspolymerization occurred, but again an irregular edge configurationresulted from polymerization shrinkage. This edge portion could beremoved by cutting but this resulted in an edge of appreciable thicknesswhich tended to catch the eyelid during movement of the latter, andcaused displacement of the lens.

These difficulties with shrinkage compensation therefore have heretoforeprecluded lens production by casting in closed mold systems and othermethods of producing contact lenses of crosslinked polymeric materialssuch as spin casting and machining and polishing have been employed.

In the spin casting process as taught in U.S. Pat. No. 3,408,429 andU.S. Pat. No. 3,496,254 the polymerizing mixture is contained in arotating open mold having a concave surface. The anterior, convexsurface of the lens is thus formed by the mold surface, and theposterior, concave surface of the lens is formed as a result ofcentrifugal forces, surface tension of the polymerizing mixture andother factors such as the size and shape of the mold, the volume of thepolymerizing mixture, the condition of the mold surface, etc. Theconcave surface of the lens thus formed is approximately parabolic inshape and many factors must be carefully controlled to producereproducible shapes. Lenses produced by spin casting usually requirepost-polymerization edge finishing and optical quality is not of thehighest since there is no truly spherical optical zone due to theaspheric nature of the posterior surface.

Most manufacturers of contact lenses of crosslinked polymeric materialsuse a traditional machining or mechanically working and polishing oflens blanks as taught in U.S. Pat. No. 3,361,858. This method has theadvantage of being able to "tailor make" lens curvatures and powers toany desired degree and to furnish high optical quality. The methodsuffers from the disadvantage of requiring highly skilled artisans forquality production.

It is the object of this invention to provide a method for producingcast lenses in a closed mold system, such lenses having the desirableoptical and fitting characteristics of machined and polished lenses.

SUMMARY OF THE INVENTION

The invention comprises a novel form of casting mold and the mode ofutilizing same to produce contact lenses. The mold comprises a maleportion, a female portion, and a flexible rim portion. The male portioncomprises a molding surface, and, in the preferred embodiments asubstantially cylindrical support segment wherein said molding surfaceis attached circumferentially around the lower circumference of thesupport segment. The molding surface has a pre-determined curvaturewhich will provide one of the surfaces of the contact lens.

The female portion similarly comprises a second molding surface and, inthe preferred embodiments, a hollow cylindrical support portion. Theinner diameter of said cylinder is substantially equivalent to theexternal diameter of the support portion of the male segment, the femalesegment, however, having a diameter just slightly greater than that ofthe male segment. The diameters are pre-determined so that there issufficient clearance for the male segment to fit into the female segmentand to permit excess monomer or other material used in the process toflow out between the two segments. The clearance, however, should not beso great as to permit the axis of the two segments to be non-aligned toa degree which would adversely affect the optical centering of the lensto be produced.

In the preferred embodiments one end of the said female portion isclosed with said second molding surface of pre-determined curvature,said molding surface providing the second surface of the contact lens tobe produced.

The flexible rim portion is integrally attached to the molding surfaceof either the male portion or the female portion in such a manner thatit is a coaxial therewith.

The mold surfaces are so arranged that one is a concave and the other isa convex. As will be seen hereinbelow all combinations which are concaveand convex curvature together with the rim portion being attached toeither, are within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 6 are exploded sectional elevations of the embodimentsof the present invention.

FIG. 1 shows a convex male molding surface with the flexible rimattached thereto and a concave female molding surface.

FIG. 2 shows a concave male molding surface and a convex female moldingsurface with the flexible rim attached to the female surface.

FIG. 3 is similar to FIG. 2 except that the flexible rim is attached tothe male portion.

FIG. 4 is an alternate embodiment of FIG. 3.

FIG. 5 is similar to FIG. 1 except that the flexible rim portion isattached to the female molding surface.

FIG. 6 shows a simplified version of the embodiment of FIG. 1.

FIG. 7 shows a compressed view of FIG. 1 wherein the rim is shown inflexed form.

In all of the figures the last two digit numbers represent equivalentitems numbered with three digits where the last two digits are the same.Thus, Item 110, Item 210, Item 310, and Item 410 all represent the malemolding portion.

In the more detailed discussion of the most preferred embodiment belowonly FIG. 1 will be discussed, and the discussion relating thereto isequally applicable to the embodiments of all of the other figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The mold comprises two portions, namely a male portion 110 and a femaleportion 130. The male portion, in the preferred embodiments, comprises asubstantially cylindrical support segment 114 having, optionally,attached to the upper end thereof a rim 112. In the preferredembodiment, because of savings in mold materials, said cylindricalportion 114 is, as shown, hollow; however, the invention should not beconsidered as being limited thereto. Support member 114 is closed bymolding surface 120 circumferentially attached to the bottom of cylinder114. The curvature of 120 is pre-determined to comply with the opticalrequirements of the lens to be produced. The curvature may be entirelyspherical or aspherical or combinations of both. Further, the surfacemay be toric in the central or optical zone; however, the peripheralportion must be symmetrical in respect to the central axis of the lensin order to achieve proper seating or mating with the rim to bediscussed herein below. In the modification of FIG. 1 a flexiblecircumferential ring 116 is located around the molding surface integraltherewith. Said ring 116 comprises an outer surface 117, an innersurface 119, and a contact edge 118.

The female portion 130 comprises, in the preferred embodiments, acylindrical support member 134 set, optionally, in a base 132 setcircumferentially thereto and a molding surface 140 set internally incylinder 134. As with respect to male molding surface 120 the curvatureof female molding surface 140 is pre-determined and may vary in the samemanner as the curvature of mold surface 120. The only limitation placedupon the mutual relationship of curvature of surfaces 120 and 140, whichwill be discussed in greater detail herein below, is that the article tobe molded therebetween shall have the general characteristics suitablefor a contact lens, namely that the article produced thereby shall havea concave surface which will contact, when in use, the eyeball of thewearer and a second, convex surface, which shall contact the internalportion of the eyelid of the wearer.

During the operation of the process which will be discussed in greaterdetail herein below, the material which will constitute the contact lensis placed in the female portion of the mold. The male portion placedinto the female portion in such a manner that tip 118 of the rim in thiscase attached circumferentially around the male molding surface 120 justtouches the surface 140 of the female molding surface. At this pointexcess molding material is squeezed out between the outer edge ofcylindrical support means 114 and the inner edge of cylindrical supportmeans 133. In the embodiment shown in the figures no runoff channels insaid cylindrical portions are shown or provided. Nevertheless, theprovision of molds having such channels is to be considered in the scopeof the present invention. They are not utilized in the preferredembodiments since the provision of such molds requires an additional,and more expensive, step in manufacturing the molds and provisionthereof has not been found to be needed.

The drawings herein are not to scale, in particular, with regard to therim segments -- say 116, and the clearance between, say 114 and 133.

The two parts of the mold containing the molding material are thensubjected to the molding processes which are discussed in detail hereinbelow. During the molding stage, the molding material will contract,this contraction may be as much as 20% of the volume of the moldingmaterial originally present between surfaces 119, 120, and 140. Sincesuch a contraction takes place in a totally enclosed space, a potentialvacuum is formed which will be counteracted by external atmosphericpressure causing the two molds 110 and 130 to move towards each other.The flexibility of rim 116 permits the molds to thus approach each othermore closely due to the flexing of rim 116 in a uniform manner. Ifdesired, external pressure can be applied to ensure that the moldingsurfaces do approach each other as closely as possible. However, theapplication of such external pressure is optional and, while in certaincases, may give rise to improved results the operation of the processeswill proceed without said external pressure. upon completion of themolding step, the molds are separated and the lens produced stripped outfrom the mold in a condition ready to use except for cleaning andpolishing of the edges. The optical surfaces -- that is to say, thecontact surfaces -- are in their desired state.

As stated herein before, the set of molds shown in FIG. 1 is the mostpreferred embodiment, in that it is the simplest of the preferredembodiments in the present invention to manufacture. Nevertheless, asstated hereinabove, the invention is in no way limited to thisembodiment. FIG. 5 shows a variation of FIG. 1 wherein the rim herein536 is integral with female molding surface 540. In this modification asin that of FIG. 1 the male surface is convex and the female surface isconcave. The upper edge 538 of ring 536 contacts male molding surface520 and the surfaces enclosing the lens creating molded material aredefined by the surfaces between the point on surface 520 contacted byedge 538, and by internal surface 539 of edge 536 together with theinternal portion of molding surface 540. The operation of the process issimilar to that described generally with respect to FIG. 1 and in moredetail herein below.

FIG. 2 shows yet another embodiment of the invention wherein the edgering 236 is attached to female molding surface 240. In thismodification, however, the female molding surface 240 is convex andtherefore, the male molding surface 220 is concave. In other respectsthe operation of the process and the mutual relationship of itscomponent parts are as before.

FIG. 3 shows a modification of the embodiment of FIG. 2 wherein theflexible ring portion 316 is attached to the male, concave portion 320rather than the female, convex molding surface 340.

In the modification of FIG. 4 a variation of the embodiment of FIG. 3 ispresented wherein the flexible edge ring 416 is actually located on theedge of molding surface 420 rather than internally as shown in themodification of FIG. 3.

In the simplified embodiment of FIG. 1 above, in FIG. 6 the cylindricalsupport member 14 of the male portion and the cylindrical support member34 of the female portion are eliminated so that the mold surfaces 620and 640 are set directly into each other. While this modification isoperative and illustrates basic features of the invention, themodifications additionally including the cylindrical support means arepreferred in view of their additional handling stability.

The advance in the art represented by the present invention depends uponthe interaction of several factors, one of which is the form of the moldset forth herein and above. The other factors are the nature of thematerials utilized to construct the mold. The material utilized for theconstruction of the mold must, under the conditions utilized in themolding procedure be sufficiently rigid to preserve the pre-determinedcurvatures of the molding surfaces. Yet, when formed in a thin ring suchas ring 116, be flexible enough to permit the contraction of the moldingvolume mentioned herein above.

It has been found that suitable materials for construction of the moldsare thermoplastic resins which are inert to the polymerizing media,which have the requisite flexibility under polymerization conditions,which do not strongly adhere to the polymerized species and which can bemolded to an optical quality surface. Especially suitable materialsinclude polyolefins such as low, medium, and high density polyethylene,polypropylene, propylene copolymers known as polyallomers, polybutene-1,poly-4-methylpentene-1, ethylene vinyl acetate and ethylene vinylalcohol copolymers, and ethylene copolymers such as polyionomers. Othersuitable materials are polyacetal resins and acetal copolymer resins,polyarylethers, polyphenylene sulfides, polyaryl sulfones, polyarylethersulfones, Nylon 6, Nylon 66 and Nylon 11, thermoplastic polyesters andvarious fluorinated materials such as fluorinated ethylene-propylenecopolymers and ethylenefluoroethylene copolymers.

The choice of a particular thermoplastic material for use in fabricationof molds is governed by polymerization conditions to be used. Ingeneral, a guide is the heat distortion temperature at 66 psi fiberstress (ASTM D648) of the plastic material. Thermoplastic molds aregenerally operable in this invention at temperatures ranging from 20° to40° C. below the heat distortion temperature up to a few degrees,suitably 10°, above the heat distortion temperature.

For example, low density polyethylene shows a heat distortiontemperature of 40°-50° C., and acceptable results under light loadingare obtained with this material at polymerization temperatures of from30° to above 70° C. Above 70° C., some distortion of optical surfacesmay occur.

Whereas, with polypropylene, which has a heat distortion temperature inthe range of 100° to 120° C., with little or no applied pressure,acceptable results are obtained at polymerization temperatures fromabout 65° to 120° C. Below 65° C., flexibility of the plastic rim is notsufficient to compensate for shrinkage, and above 120° C., distortion ofoptics occurs.

High polymerization temperatures may be used for materials such asnylons, polyphenylene sulfides, polysulfones and fluorinated polymersshowing higher heat distortion temperatures.

In addition, it is possible to operate at lower polymerizationtemperatures by increasing the "load" or mold closing pressure applied.For example, shrink marks or surface voids are likely to appear in castlenses made with the polypropylene molds of this invention at apolymerization temperature of below 65° C. at light closing pressureapplied to the mold; however, if the closing pressure is increased to,for example, 10 psi, (calculated on the total mold area) lenses freefrom surface blemishes are obtained. Thus the requisite flexibility ofthe mold rim may be obtained through a combination of polymerizationtemperature and closing pressure.

It is noted that the male mold member, say, 110 has the rim 116integrally formed at the periphery of the male molding surface 120. Thejunction of the base of the rim 116 with the surface 120 forms theposterior portion of the edge of the lens, while the mating line 118 ofthe rim with the female mold member 140 forms the anterior shape of theedge. The overall thickness of the edge thus formed is the "height" ofthe rim 116--i.e., outer edge 118 to inner edge 113--less the distancethe rim flexes to compensate for the shrinkage that occurs onpolymerization. Depending on the edge thickness desired, the height ofthe rim 116 may vary from about 0.05 mm for a very thin edge, to as muchas 0.3 mm for a rather thick, rounded edge. In a typical example, theheight of the rim 116 from the edge 118 to edge 113 of the curve is 0.10mm. If a polymerizing mixture which has a volumetric shrinkage of 20% isemployed, then the rim must flex sufficiently to allow the thickness ofthe edge to contract to 0.08 mm. This flexing takes place generally byan inward bending as illustrated in FIG. 7. Similar flexing occurs inthe embodiments of FIGS. 2-6.

It is desirable that the apex of the rim be as thin as possible tominimize the irregularity of the "mating or parting line". In practice,the thickness of the apex of the rim is held below 0.04 mm, andpreferably below 0.01 mm. The rim is very delicate and the male moldmember must be handled with care to avoid damage.

The outside diameter of the male mold half must be sufficiently smallerthan that of the female half to permit escape of excess of the materialto be polymerized upon closing the mold. Tapering of the male and femalehalves aids in removal of excess material but is not critical. Ingeneral, the male half is preferably from 0.1 to 0.3 mm smaller indiameter than the female half. If the size difference is too great, forexample 0.5 mm, then alignment of the optical centers of the two moldhalves becomes problematic, although the invention is still operable.

In the practice of this invention, metal molds, designated to producethe desired male and female thermoplastic molds are fabricated bytraditional machining and polishing operations. These metal molds arethen used in injection or compression molding machines to produce aplurality of thermoplastic molds which in turn are used to cast thedesired lenses from polymerizable or vulcanizable mixtures. Thus, a setof metal molds can yield a large number of thermoplastic molds which, inturn, yield an even larger number of lenses since the thermoplasticmolds may be reused if handled with care. This constitutes aconsiderable saving over the traditional method of machining andpolishing individual lenses, since the machining and polishingoperations are carried out only on the original metal molds.

The design of the lenses produced by this invention is not restricted toany particular set of parameters. Both anterior and posterior surfacesof the lenses may consist of entirely spherical curves or asphericalcurves or combinations of both. For example, the central portion of thelens may consist of spherical curves on both the anterior and posteriorsurface, and the periphery of the anterior surface may consist of asteeper or flatter spherical curve, and the periphery of the posteriorsurface may be aspheric to achieve improved fitting characteristics.

In addition, one or both of the surfaces may be toric in the central oroptical zone; however, the peripheral portion must be symmetrical withrespect to the central axis of the lens to achieve proper seating ormating of the integral rim.

Monomer, prepolymer or vulcanizable mixtures particularly useful in thepractice of this invention include hydrophobic acrylic esters, suitablylower alkyl acrylic esters, the alkyl moiety containing 1-5 carbonatoms, such as methyl acrylate or methacrylate, ethyl acrylate, ormethacrylate, n-propyl acrylate or methacrylate, isopropyl acrylate, ormethacrylate, isobutyl acrylate or methacrylate, n-butyl acrylate ormethacrylate, or various mixtures of these monomers. For increaseddimensional stability and resistance to warpage the above monomers ormonomer mixtures may be further admixed with a minor proportion of di orpolyfunctional polymerizable species to cause cross linking of thepolymeric matrix as polymerization proceeds. Examples of such di- orpolyfunctional species include: divinyl benzene, ethylene diacrylate ormethacrylate, propylene glycol diacrylate or methacrylate and acrylateor methacrylate esters of the following polyols, triethanol amine,glycerol, pentaerythritol, butylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, mannitol, sorbitol and thelike. Other cross linking monomers may include N,N-methylene-bis-acrylamide or methacrylamide, sulfonated divinylbenzene, and divinyl sulfone.

Further, the above monomers or mixtures thereof may be further mixedwith linear polymeric species which are soluble therein as long as theviscosity of the solution or "casting syrup" formed thereby does notbecome sufficiently great that difficulty in removing bubbles therefromis encountered.

Other monomeric materials suitable for producing lenses via thisinvention are hydrophilic monomer mixtures forming three dimensionalcross linked networks such as those disclosed in U.S. Pat. No.3,822,089. In addition to the hydrophilic acrylic monomers disclosed inthe aforementioned patent, useful materials include mono or di N-alkylsubstituted acrylamides or methacrylamides, N-vinyl pyrrolidone, alkylether acrylates and methacrylates, and vulcanizable silicone fluids orelastomers. The alkyl moieties are suitable lower alkyl groups of 1-5carbon atoms.

With the hydrophilic monomer or mixtures thereof, it is essential that a3-dimensional cross linked network be formed since the polymerizedmaterials absorb water and become soft and flexible and would lack shaperetention if not cross linked. Suitable cross linking monomers are thoselisted above for the hydrophobic acrylic esters.

Polymerization of monomer mixtures is usually carried out with freeradical catalysts of the type in common use in vinyl polymerization.Such catalyst species include organic peroxides, percarbonates, hydrogenperoxides, and inorganic materials such as ammonium, sodium, orpotassium persulfate. Polymerization using such catalysts may occur attemperatures between ambient temperature -- i.e., ca 20° C. and about120° C. -- depending on the speed of polymerization desired.

Polymerization may also occur between monomer or prepolymer mixturesunder the influence of elevated temperatures or radiation (U.V., X-ray,or radioactive decay).

With silicone elastomers, vulcanization may take place via a freeradical curing mechanism, or, in the case of two part so called RTVcompounds vulcanization may occur through displacement or condensationreactions.

The following examples serve to further illustrate the invention.

EXAMPLE 1(a) Formation of Molds

Female high density polyethylene molds were prepared by injectionmolding on a convex male steel mold having an outside diameter of 12.0mm, a central radius of curvature of 7.50 mm with a chord diameter of10.0 mm and a peripherical radius of curvature of 7.00 mm. Male highdensity polyethylene molds were prepared by injection molding in aconcave steel mold having an inside diameter of 11.9 mm, central radiusof 7.00 mm with a chord diameter of 11.0 mm, and a peripheral curvehaving a radius of 12.5 mm. The periphery of the curved mold surface wasrecessed to provide a peripheral rim 0.01 mm wide at the apex extending0.12 mm from the edge of the curve. Radiuscope measurement showed thecentral radius of curvature of the female concave molds to be 7.43±0.04mm and the inside diameter measured 12.1 mm. The outside diameter of themale molds was 11.8 mm, and the central radius of curvature was6.95±0.03 mm.

EXAMPLE 1(b) Formation of Lens

Ten concave female molds were placed on a flat surface with the cavityprojecting upward. A solution consisting of carefully purified2-hydroxyethyl methacrylate, 100 parts; distilled water, 30 parts;ethylene glycol dimethyl ether, 25 parts; triethylene glycoldimethacrylate, 0.4 parts; and di-isopropyl percarbonate, 0.2 parts; wasprepared by thorough mixing. One-half ml. of the solution was placed inthe female mold, and the male mold halves were slowly inserted todisplace excess solution and to displace any bubbles. Slight pressurewas applied on the male halves to ensure seating of the rim. The filledmolds were then placed in a circulating air oven at 45° C. for 11/2hours. After cooling to room temperature, the molds were opened, the"ring" of polymerized material filling the cylindrical void in theannulus between the mold halves was removed, and the flexible lenseswhich adhered lightly to the male half of the mold were carefully peeledoff. After soaking in physiological saline to leach the ethylene glycoldimethyl ether from the lenses, the lenses were examined.

The edges were smooth and evenly formed, requiring no further treatment,and the surfaces were smooth and unblemished. The lenses had a centerthickness of 0.19±0.02 mm, optical powers of -2.50 to -2.75 diopters,and diameter of 12.0 mm.

EXAMPLE 1(c) Formation of Lens

A solution consisting of purified 2-hydroxy-ethyl methacrylate, 55parts; N,N-dimethyl acrylamide, 45 parts; water, 30 parts; diethyleneglycol dimethyl ether, 20 parts; methylene-bis acrylamide, 0.3 parts;and diisopropyl percarbonate, 0.3 parts; was cast in the molds ofExample 1(a), in a manner identical to that of Example 1(b).

Unblemished lenses having a center thickness of 0.21±0.03 mm, edgethickness of 0.10±0.02 mm, diameter of 13.0 mm, and optical powers offrom -2.25 to -2.50 diopters were obtained after equilibration in 0.9%saline solution. The larger size and somewhat lower optical power ofthese lenses over those of Example 1 is caused by the higher swellingcoefficient of this polymer composition in water.

EXAMPLE 2(a) Formation of Molds

Female molds were prepared using an ethylenevinyl acetate copolymer(having a 10% vinyl acetate content) by injection molding on a convexmale steel mold having an outside diameter of 8.3 mm, central radius ofcurvature of 8.60 mm at a chord diameter of 6.5 mm and a peripheralradius of curvature of 7.55 mm. Male molds were produced from the samecopolymer by injection molding in a female steel cavity having a centralconcave radius of curvature of 7.50 mm with a chord diameter of 7.8 mmand a peripheral radius of curvature of 9.50 mm. The periphery of theconcave mold was recessed to provide a rim on the molded part protruding0.1 mm from the edge of the curved surface with an apex thickness of0.015 mm. The inside diameter of the concave steel mold was 8.0 mm.

The inside diameter of the injection molded female cavities was 8.2 to8.4 mm and the central radius of curvature was 8.55±0.05 mm. The outsidediameter of the male convex plastic molds was 7.9 mm and the centralradius of curvature was 7.45±0.03 mm.

EXAMPLE 2(b) Formation of Lenses

A solution consisting of methyl methacrylate, 98 parts; ethylenedimethacrylate, 20 parts; and di-t-butylcyclohexylperoxy dicarbonate,0.3 parts; was prepared, and 0.3 ml of the solution was introduced intoeach of 10 of the upward facing concave female molds. The male moldswere slowly lowered into cavities to displace air and excess monomermixture. The male molds were pressed lightly to ensure seating of therim on the concave female mold surface and the molds were placed in acirculating air oven at 60° C. for 11/2 hours. The molds were thencooled and opened.

Lenses free from defects having a diameter of 7.9 mm, central thicknessof 0.10±0.02 mm, central posterior radii of curvature of 7.47±0.4 mm andoptical power in the range of -7.50 to -8.50 diopters were obtained.

These lenses exhibited superior resistance to warpage and could beflexed without permanent deformation as opposed to lenses of the samedimensions fabricated from non-cross linked polymethyl methacrylate.

EXAMPLE 3(a) Formation of Molds

Using the metal molds of Example 1a, a female and male thermoplasticmolds were prepared using Nylon-11. Female concave nylon molds having aninside diameter of 12.0 mm and a central radius of curvature of7.48±0.03 mm were obtained. Male nylon molds having an outside diameterof 11.8 mm and a central convex radius of curvature of 6.99±0.03 mm wereobtained. The peripheral rim projected 0.14 mm from the edge of thecurved surface and was less than 0.01 mm thick at its apex.

EXAMPLE 3(b) Formation of Lenses

A two part room temperature vulcanizable transparent methyl siliconeliquid was mixed, and 0.4 cc of the mixture was placed in the upwardfacing concave female molds. The male molds were inserted to displaceexcess fluid and the molds were lightly pressed to ensure seating of therim. Molds were placed in a circulating air oven at 135° C. for twohours.

After cooling the molds were opened and lenses measured. The centerthickness was 0.22±0.02 mm, the edge thickness was 0.11±0.02 mm, and theoptical power ranged from -2.00 to -2.50 diopters.

I claim:
 1. A mold for producing a contact lens comprising:a maleportion including a substantially cylindrical support portion and afirst molding surface having a principal longitudinal axis, said moldingsurface having a pre-determined curvature to form a first surface ofsaid desired contact lens; a female portion including a second moldingsurface having a principal longitudinal axis having a pre-determinedcurvature to form a second surface of said desired contact lens, saidfemale portion comprising a hollow cylindrical portion having an openupper end and a closed lower end; and, a flexible rim portion beingattached circumferentially to one of said molding surfaces and having anaxis common with the principal longitudinal axis of the mold portion. 2.A mold in accordance with claim 1 wherein the rim portion is attached tothe male portion.
 3. A mold in accordance with claim 1 wherein the rimportion is attached to the female portion.
 4. A mold in accordance withclaim 2 wherein the male portion has a substantially convex moldingsurface and the female portion has a substantially concave moldingsurface.
 5. A mold in accordance with claim 3 wherein the male portionhas a substantially convex molding surface and the female portion has asubstantially concave molding surface.
 6. A mold in accordance withclaim 2 wherein the male portion has a substantially concave moldingsurface and the female portion has a substantially convex moldingsurface.
 7. A mold in accordance with claim 3 wherein the male portionhas a substantially concave molding surface and the female portion has asubstantially convex molding surface.
 8. A mold in accordance with claim1 wherein the mold is constructed of thermoplastic material.
 9. A moldin accordance with claim 8 wherein the thermoplastic material isselected from the group consisting of polyolefins, olefin copolymers,polyacetal polymers and copolymers, polyaryl ethers, polyphenylenesulfide, polyaryl sulfides, polyarylethersulfones, polyamides,polyesters, and fluorinated polymers.
 10. A mold of claim 1 forproducing a contact lens comprising:a male portion including asubstantially cylindrical support portion having a principallongitudinal axis and a first molding surface attached circumferentiallyto said cylindrical support portion, said molding surface having apre-determined curvature dimensional to form the surface of said desiredcontact lens; a female portion comprising a hollow cylindrical portionhaving a principal longitudinal axis and having an open upper end and aclosed lower end, the internal diameter of said female cylindricalportion being sufficiently greater than the external diameter of saidmale support portion to permit frictionless insertion of the maleportion thereinto, said female portion being circumferentially closed atthe lower end thereof by a second molding surface having apre-determined curvature to form a second surface of said desiredcontact lens; and, a flexible rim portion being attachedcircumferentially to one of said molding surfaces and having an axiscommon with the principal longitudinal axis of the mold portion.
 11. Amold in accordance with claim 1 wherein the rim portion is integral withsaid molding surface.
 12. A mold in accordance with claim 11 which isconstructed of thermoplastic material.
 13. A mold in accordance withclaim 12 wherein said integral rim portion is flexible inwardly towardsthe axis of the molding surface.
 14. A mold in accordance with claim 12wherein said integral, flexible rim has a height of from about 0.05mm toabout 0.3mm.
 15. A mold in accordance with claim 12 wherein saidintegral, flexible rim has an apex thickness of 0.04mm or less.
 16. Amold constructed of thermoplastic material for producing a contact lenscomprising:a male portion including a first molding surface having aprincipal longitudinal axis, said molding surface having apre-determined curvature to form a first surface of said desired contactlens; a female portion including a second molding surface having aprincipal longitudinal axis having a predetermined curvature to form asecond surface of said desired contact lens; and a rim portion flexibleinwardly towards the axis of the molding surfaces attachedcircumferentially to, and integral with, one of said molding surfacesand having an axis common with the principal longitudinal axis of themold portion; whereby said flexible rim allows for relative movementbetween said male portion and female portion when said portions are incontact with each other, said rim flexing inwardly towards the axis ofsaid molding surfaces.
 17. A mold constructed of thermoplastic materialfor producing a contact lens, said mold including:a male portionincluding a substantially cylindrical support portion having a principallongitudinal axis and a first molding surface attached circumferentiallyto said cylindrical support portion, said molding surface having apre-determined curvature to form the surface of said desired contactlens; a female portion comprising a hollow cylindrical portion having aprincipal longitudinal axis and having an open upper end and a closedlower end, the internal diameter of said female cylindrical portionbeing sufficiently greater than the external diameter of said malesupport portion to permit frictionless insertion of the male portionthereto; said female portion being circumferentially closed at the lowerend thereof by a second molding surface having a pre-determinedcurvature to form a second surface of said desired contact lens; and anintegral rim portion flexible inwardly towards the axis of the moldingsurfaces attached circumferentially to, and integral with, one of saidmolding surfaces and having an axis common with the principallongitudinal axis of the mold portion; whereby said flexible rim allowsfor relative movement between said male portion and said female portionwhen said portions are in contact with each other, said rim inwardlyflexible towards the axis of said molding surfaces.
 18. A moldconstructed of thermoplastic material for producing a contact lenscomprising:a male portion including a first molding surface having aprincipal longitudinal axis, said molding surface having apre-determined curvature to form a first surface of said desired contactlens; a female portion including a second molding surface having aprincipal longitudinal axis having a pre-determined curvature to form asecond surface of said desired contact lens; and a rim portion flexibleinwardly towards the axis of the molding surfaces attached adjacent tothe circumference of one of said molding surfaces and having an axiscommon with the principal longitudinal axis of the mold portion; wherebysaid flexible rim allows for relative movement between said male portionand female portion when said portions are in contact with each other,said rim flexing inwardly towards the axis of said molding surfaces.